Two nice list blogs keeping track of apps being updated for iOS 7:
Presumably these will only be able to keep up with the forthcoming avalanche of updates for a short time, but scrolling through them immediately reveals some interesting issues.
They make clear that the wholesale and unmeasured adoption of the aesthetic tropes of iOS 7 isn't enough on its own to suddenly make your app look fresh and great. If it didn't look good beforehand, throwing in some translucency and line art icons will more than likely make it look busier and more muddled than it did before.
This app was easier to understand before it was iOS 7'd
Equally, even if your app did look great before, swapping skeumorphic affordances out for flat colours and replacing icons with words might make it both less appealing to look at and harder to use.
Embracing Apple's new iOS 7 interface guidelines at the time of your visual refresh is your best hope to avoid these problems and ensure the experience your users encounter matches the new coat of paint you've applied.